Many physiological processes require that cells be in close contact with other cell populations and/or the extra-cellular matrices. These processes of adhesion are however necessary for activation, migration, proliferation and cell differentiation. Several families of cellular adhesion molecules (CAMs) that play an essential role in normal and patho-physiological processes mediate cell-cell-matrix interactions.
The process of cellular adhesion, essential for activation of neutrophils, is accompanied by the release of cytokines, among which are IL-8 and MCP-1 which allow amplification of the inflammatory process (see: Huang CD et al, Chang Keng J Hsueh, 22, 392, 1999; and B. Walzog et al, FASEB J., 13, 1855 1999).
The chemokines, in their turn, are distinguished, functionally, from other cytokines by the cellular specificity of their action: each of them regulates the migration and the function of a single cellular species in a specific way. Thus, while MCP-1 influences and directs the movements of monocytes, IL-8 carries out the pre-eminent role of neutrophil chemo-attracting factor.
This is confirmed by the presence of high concentrations of IL-8 in the sites of inflammation and in the surrounding fluid, measured in the course of many acute pathologies mediated by neutrophils, the prevention of serious tissue damage and the reduced infiltration by neutrophils observed after administration of IL-8 antibodies in the course of experiments on animal models showing neutrophil-dependent pathologies (see: Yang X D et al, J. Leukoc. Biol 66, 401, 1999). Typical clinical situations where neutrophil activation plays a prevailingly pathological role are damage resulting from cerebral reperfusion (Stanimirovic D and Satoh K, Brain Pathol., 10, 113 2000) and from ischemia and reperfusion of the myocardium.
These observations have confirmed the hypothesis that IL-8 constitutes the main mediator of neutrophil induced tissue damage to such an extent as to propose interleukin-8 as the optimal target for therapeutic intervention in neutrophil-dependent pathologies (N. Mukaida et al, Inflammation Res. 47 (Suppl. 3) S151, 1998). For this reason, as an alternative to the use of anti-IL-8 antibodies, low-molecular weight substances could be of great clinical interest and usefulness, said substances being able to insert into the inter- and intra-cellular signal transmission circuits, and to inhibit the migration of human neutrophils stimulated by IL-8 and similar substances (GRO-α, β, γ; ENA-78, NAP-2, GCP-2).
This is more current now that the determining role that the activation of certain kinases and tyrosine-kinases play in the dynamics of the IL-8 dependent chemotaxis event is becoming clearer.
For a long time it was suspected that the activation of certain tyrosine-kinases was the trigger event of the chemotaxis phenomenon after Yasui et al (J. Immunol. 152, 5922, 1994) demonstrated that complete inhibition of the PMN chemotaxis followed the inhibition of the activity of these enzymes.
More recently, the dramatic reduction of PMN chemotaxis, induced by a variety of chemokinic factors, observed in genetically modified rats deficient in the enzyme phosphoinositide 3-kinase (IP3K, Hirsch et al, Science, 287, 1049, 2000; Sasaki et al, Science, 287, 1040 2000), allows this enzyme to be characterized as the leader-kinase—primus movens of the successive cascade of events—and strengthens the belief in the specific and determining role carried out by the enzymatic processes of phosphorylation.
In the chemotaxis phenomena induced by interleukin-8 on PMN, besides phosphoinositide 3 kinase, an equally important role seems to be played by PyK2 (proline-rich tyrosine kinase) whose activation is essential for the development of the concomitant processes of cellular adhesion. In its turn, the process of activation of Pyk2, induced by IL-8 in PMN, is an IP3K dependent process that seems to happen and be localized in the areas of the cellular membrane dedicated to focal adhesion (Clark et al Science, 268, 233, 1995: Avraham et al, Blood, 88, 417, 1996), in direct contact with the cytoskeleton proteins involved in the adhesion phenomenon (e.g. vinculine, α-actine etc).
Also in the light of recent discoveries, it is believed that the therapeutic potential of new low-molecular weight molecules called to interfere with IL-8 dependent chemotaxis phenomenology is increased by some inhibitory activity towards the factors that promote adhesion and/or antagonist activity towards some integrines such as very late antigen 4 (VLA-4), LPAM-1, to block their linking to their ligands in order to usefully prevent ab initio the start of that cascade of events which, starting from the of intra-cellular adhesion processes, translate into neutrophil activation.
Recently N-acylsulfonamides and R-2-arylpropionic acid amides have been described (WO 00/24710 and PCT/EP01/01285, respectively), that are characterized by the selectivity of their inhibitory activity of IL-8-stimulated chemotaxis of human neutrophils. In the course of studies directed to define their molecular mechanisms of action, it was observed that they show a very substantial (70%–80% of inhibition), dose-dependent, inhibitory activity towards Pyk2-tyrosine-kinase activity for concentrations ranging from 10−7 to 10−8 M not dissimilar from the concentrations which show an effective inhibition of IL-8 dependent chemotaxis.
Furthermore, the activity of said amides and N-acylsulfonamides of R-2-arylpropionic acids seems to be totally independent from their involvement in the inhibition of (COX-1 and/or COX-2) cyclooxygenase dependent inflammatory processes.
There is also accumulated evidence that the inhibition of prostaglandin (PG) synthesis by (S)-enantiomers of 2-arylpropionic acids and certain 2-aryl-acetic acids can, in the long term, negatively reflect on the dynamics of the neutrophil-dependent inflammatory process, where inhibition of PG synthesis, and therefore of PGE2 removes a control factor of the endogenous synthesis of TNF-α. Accordingly, in competition with the same IL-8, TNF-α may contribute, with IL-6 and IL-1 cytokines and with the adhesion molecules (E-selectine, ICAM-1 and C-reactive protein) to worsen the entity and severity of tissue damage in the course of acute myocardium infarct (R. Pudil et al, Clin Chim Acta, 280, 127, 1999).